Patient handling mattresses are known in the art which include at least two flexible material sheets that together define a plenum chamber, with at least one sheet being perforated with small pinholes over at least a central surface area, and which open up directly to the interior of the plenum chamber. Such prior art mattresses are used by arranging the perforated sheet so that it faces an underlying fixed, generally planar support surface such as a floor or table. When the mattress is charged with pressurized air the escape of air under pressure through the pinholes acts initially to jack a load placed upon the mattress above the perforated flexible sheet, and thereby creates an air bearing of relatively small height between the underlying fixed, generally planar support surface and the perforated flexible sheet.
For example, in U.S. Pat. No. 4,517,690, issued to Wegener, an air pallet is disclosed that is formed from upper and lower thin flexible film sheets sealed at their edges to form a plenum chamber. Wegener's air pallet functions to move a load with minimal friction over an underlying generally planar fixed support surface. The bottom thin flexible material sheet is perforated by small diameter perforations such as pin holes at the load imprint area.
In U.S. Pat. No. 5,561,873, issued to Weedling, provides an inflatable flexible pallet within which an array of structurally interrelated inflatable chambers are formed to support a load when inflated. The flexible pallet is configured to resist lateral and longitudinal shrinkage of the load support surface, as well as ballooning and hot dogging. Rotational instability is also reduced by providing a greater load surface support area.
In U.S. Pat. No. 6,073,291, issued to Davis, an inflatable medical patient transfer apparatus is disclosed that has a combination of transverse partition members and a raised perimeter section to reduce deleterious ballooning and uneven inflation as well as quick emergency deflation. Additional differentially inflatable patient rolling chambers are disclosed on the top of the transfer apparatus to provide assistance to medical personnel in beginning to roll patients reclining or lying upon the transfer apparatus, particularly in a deflated condition on a hospital bed.
In U.S. Pat. No. 7,107,641, issued to Davis, a double chambered transfer mattress is provided capable of partial deflation that includes a top inflatable mattress and a bottom inflatable mattress that are separated by a common wall from one another. A selectable inlet/outlet valve is arranged for airflow communication between an interior chamber of the bottom inflatable mattress and a source of pressurized air. A one-way valve is positioned through the common wall so as to provide selective air flow communication between the top inflatable mattress and the bottom inflatable mattress so that when the inlet/outlet valve is opened, so as to deflate the bottom inflatable mattress, the one-way valve is actuated so as to prevent deflation of the top inflatable mattress.
All of the foregoing devices have suffered from an inability to be used on a patient transfer vehicle, e.g., a typical wheeled hospital bed or gurney, when fully or even partially inflated. Such patient transfer vehicles often include a frame, a patient pallet supported by the frame, and a pair of side rails that are movably coupled to the frame for movement between a raised position and a lowered position relative to the patient pallet's surface. When an inflated prior art transfer mattress is placed upon the patient pallet's surface, and an attempt is made to lift the side rails into their raised position, they collide with the margins of the inflated transfer mattress. This has required the complete deflation of such transfer mattresses while resident upon a patient transfer vehicle, resulting in discomfort for the patient.